1. Field of the Invention
The present invention relates to a tube fitting, and particularly relates to a tube fitting which can be connected with a soft or semi-hard tube without causing leakage.
2. Description of the Related Art
As illustrated in FIGS. 24 and 25, conventional tube fittings have been known which are designed to be connected with a soft or semi-hard tube, for example a resin tube. The tube fitting illustrated in FIG. 24 comprises a tubular body 110, an annular clamping member 120, a releasing member 130, and a sealing ring 140. The body 110 includes a regulatory surface 112 on the inner peripheral surface, regulatory surface 112 which extends in the centripetal direction as an end opening 111 comes near, and an axial bore 113 into which a tube 150 is fitted via the opening 111. The clamping member 120 is disposed slidably in the axial direction on an inner side with respect to the regulatory surface 112 in the axial bore 113. The clamping member 120 includes a plurality of arms 125 which extend from a tubular end portion 124 in the axial direction, a claw 122 disposed at the free end of the arms 123, and an outer peripheral portion 123, formed in an annular shape. The claw 122 has an inclined surface 121 which projects in the centripetal direction as the opening 111 moves away and which engages with an outer peripheral surface of the tube 150 fitted into the axial bore 113 via the opening 111. The outer peripheral portion 123 contacts with the regulatory surface 112 of the body 110, and thereby it is pressed in the centripetal direction by the regulatory surface 112 so as to press the claw 122 onto the outer peripheral surface of the tube 150. The releasing member 130 includes a tubular base 131 and a leading end 132. The tubular base 131 is disposed slidably in the axial direction of the axial bore 113 on the side of the opening 111. The sealing ring 140 is an O-ring made from rubber, and it is disposed between the base 131 and the leading end 132 of the releasing member 130.
In this conventional tube fitting, the tube 150 is fitted into the axial bore 113 via the opening 111, and it is later pulled back. Then, the outer peripheral portion 123 of the clamping member 120 is brought into contact with the regulatory surface 112 disposed in the axial bore 113 of the body 110, and it is pressed in the centripetal direction. Thus, the claw 122 is pressed onto the outer peripheral surface of the tube 150, and it pinches and engages with the outer peripheral surface of the tube 150. By the engagement between the claw 122 and the tube 150, the tube 150 is engaged with the body 110. The sealing ring 140 seals between the outer peripheral surface of the tube 150 and the inner peripheral surface of the axial bore 113 of the body 110. On the other hand, when the base 131 of the releasing member 130 is pressed into the axial bore 113, the base 131 pushes the leading end 132 in the axial direction by way of the sealing ring 140. Accordingly, the front end of the leading end 132 is brought into contact with the inclined surface 121 of the clamping member 120, and then the inclined surface 121 is urged to the inner side of the axial bore 113 in the centrifugal direction. Consequently, the claw 122 of the clamping member 120 is moved in the centrifugal direction, and it is separated from the outer peripheral surface of the tube 150. As a result, the tube 150 is released from the clamping member 120, and it can be pulled out of the axial bore 113 of the body 110.
The other conventional tube fitting illustrated in FIG. 25 comprises a tubular body 210 including an axial bore 213, an annular clamping member 220, a sealing ring 240, and an inner pipe 260. The body 210 has an opening at an end into which an annular end cover 214 is screwed coaxially. The end cover 214 has a regulatory surface 212 which extends in the centrifugal direction as it goes to the inner side of the axial bore 213. The inner pipe 260 is coaxially engaged with and fixed to the inner peripheral surface 213 of the body 210 at the end. Thus, on one of the sides of the body 210, there is formed a tubular groove 216 between the outer peripheral surface of the inner pipe 260 and the inner peripheral surface of the axial bore 213 of the body 210. The clamping member 220 and the sealing ring 240 are held coaxially in the tubular groove 216 whose opening end is plugged by the end cover 214.
In this conventional tube fitting, the clamping member 220 and the sealing ring 240 are disposed in the axial bore 213 of the body 210, and accordingly there is formed a tubular space between the outer peripheral surface of the inner pipe 260 and the clamping member 220 as well as the sealing ring 240. The tube 250 is fitted into the tubular space. In a manner similar to the conventional tube fitting illustrated in FIG. 24, the clamping member 120 is engaged with the outer peripheral surface of the tube 250 at its claw 221, and accordingly the tube 250 is engaged with the body 210 when the tube 250 is pulled back in the opposite direction.
Additionally, in this another conventional tube fitting, since the tube 250 is held between the clamping member 220 and the inner pipe 260, it is clamped with a strong clamping force. Further, when the annular end cover 214 is rotated with respect to the body 210 in the direction opposite to the screwing direction, the end cover 214 can be separated from the body 210. As a result, the tube 250 can be pulled out of the body 210.
In the conventional tube fitting illustrated in FIG. 24, dust, dirt or the like are likely to remain at the sealing ring 140. Accordingly, when the tube 150 is pulled out and it is again fitted into body 110 in order to engage therewith, this conventional tube fitting suffers from the improper sealing at the sealing ring 140.
The other conventional tube fitting illustrated in FIG. 25 requires a large amount of labor to disengage the tube 250 from the body 210. Similar to the first conventional tube fitting, dust, dirt or the like are likely to remain at the sealing ring 240 so that the sealing is inadequate.